Optical module with multiplexer

ABSTRACT

This invention discloses an optical module with multiplexer for a remote of an IMT-2000 digital optical repeater. The functions of an optical transmitting part of the digital optical repeater according to the present invention is data donation through a forward link, data add/drop in each sector, data summing in respective sectors and data transmission through a reverse link. This invention discloses an optical module with multiplexer that is capable of implementing the optical transmitting part&#39;s function effectively by using a signal framing, scrambling, add/drop and PLL circuits with high Q value.

PRIORITY

This application claims priority to applications entitled “An OpticalModule With Multiplexer” which were filed with the Korean IntellectualProperty Office on Feb. 25, 2002 and filed as PCT application Ser. No.PCT/KR03/00367 on Feb. 25, 2003, the contents of each of which arehereby incorporated by reference.

BACKGROUND

This invention relates to an optical module with multiplexer for remoteequipment in an IMT-2000 digital optical repeater network.

To reduce the number of base stations in a mobile telecommunicationnetwork, an analog type repeater has been used until now. Nowadaysdigital type repeaters are beginning to be used, having the followingmerits, i.e. for IMT-2000 service, a number of repeaters can beconnected in cascade, the total distance in the repeater network can bewidely expanded, the add/drop control at every repeater can be doneflexibly, the time delay in the various network can be compensated, andthe monitoring and controlling of transmission environment can beprocessed by software.

In the digital type repeater, since digitalizing CDMA signals combiningthe signals from multiple subscribers allows a large volume of data tobe transmitted, an effective optical transmission and time divisionmultiplexing (TDM) is very important factor in an IMT-2000 network.However, the type of the digital optical repeater has not beenstandardized until now, and general methods for multiplexing have notbeen formed.

FIG. 1 shows a general network structure of an IMT-2000 digital opticalrepeater. In FIG. 1, the optical transmission is bi-directional over asingle fiber. In IMT-2000 systems, three sectors are used and 4 FAs(frequency allocations) are allocated to each sector. As a donor andmany remotes share their signal bandwidth, the donor distributes thesame data to many remotes along with forward direction data. The remotestransmit the data along with reverse direction data and re-transmit themafter summing the transmitted data to the signals received from a localantenna in respective sectors. Of three sectors, only one assignedsector signal is processed at each remote. The remote can have multiplesub-branches in addition to a main branch.

The general structure of an optical transmission part for the remote isshown in FIG. 2. The optical signals (FOR) transmitted over a forwardlink by the donor are delivered through a WDM (Wavelength DivisionMultiplexer) coupler (102) is transmitted into an opticalreceive-demultiplexing module (103). The optical receive-demultiplexingmodule (103) outputs forward linked payload data D (α, β, γ)_(FWD) byprocessing of optical receiving and demultiplexing.

The payload data means a source data to be transmitted through theoptical path after digital processing and coding of the CDMA signalscombining multiple subscribers' signals in a digital optical repeater α,β, γ represent the three respectively [respective?] sectors. The payloaddata are transformed to the signals FOT1, FOT2, which are replicas ofFOR signals and transmitted over a main branch and a sub-branch throughan optical transmission and multiplexing modules (105, 106) and WDMcouplers (107, 108).

An optical switch (101) is applied to the main branch and executes afunction for bypassing signals to the next remote after skipping over atroubled remote, for example when a power failure in a remote precludessignal transmission to the next remote. In this bypassing case, it isrequired that optical signals are transmitted over 2 span optical links.Therefore, as for the main branch, an optical link having a longdistance transmitting ability compared to the sub-branch should beconsidered. For example, it is possible to realize this case by using anoptical splitter and setting a power ratio through a grading method like2:1, rather than 1:1.

In each remote, of the payload data D (α, β, γ)_(FWD) only payload dataD₀ (−)_(FWD) of one selected sector for a local remote is dropped and apayload data D₀ (−)_(RVS) of one sector is added at the same time.

The adding means adds the local payload data with a payload data D₁ (α,β, γ)_(RVS) obtained from the main branch and a payload data D₂ (α, β,γ)_(RVS) obtained from the sub-branch through the optical receivingdemultiplexing module (112, 113) and transmits them in the reversedirection through an optical transmit multiplexing module (109).

Since the optical fiber lengths of the main branch and the sub-branchare not fixed, the phase of the payload data D₀(−)_(RVS) correspondingto a local remote, the payload data D₁ (α, β, γ)_(RVS) from the main,and the payload data D₂(α, β, γ)_(RVS) from sub-branch are not the same.Therefore, these phases should be aligned before summing them. So, eachpayload data phase is aligned through a phase aligner (111) and thepayload data becomes D₁ (α, β, γ)_(RVS), D₂ (α, β, γ)_(RVS) and D₀(−)_(RVS), respectively.

The summed payload data in respective sectors D_(S)(α, β, γ)_(RVS) aretransmitted in the reverse direction through an optical transmissionmultiplexing module (109) and a WDM coupler (102). But until now, anoptical module with multiplexer to realize an optical transmission parthaving a data signal multiplexing function for a remote and an opticaltransmission/receiving function has not been disclosed.

A conventional system is described in Korean patent publication number10-2001-18675, entitled “An Apparatus For Data Processing To The ReverseDirection Link In A Digital Optical Repeater And The Method Thereof”,whose applicant is SK Telecom Inc.

But the digital optical repeater according to the disclosed functions ofsuch conventional systems for an A/D converting, D/A converting, opticaltransmission, multiplexing, demultiplexing and adding (or summing),which are well known to the skilled person in this field, fails todisclose a detailed structure.

Another system is described in Korean patent publication number10-2001-755, entitled “A Digital Signal Splitting TelecommunicatingSystem For CDMA”, whose applicant is Ino System Co., Ltd. This systemdiscloses a step for digital signalization of CDMA analog signals and aWDM method using an optical path in an optical repeater, but does notdisclose a module for optically transmitting the digitalized data.

Another system is described in Korean patent publication number10-2001-48227, entitled “A Cascade Type Digital Optical Repeater”, whoseapplicant is Mobitech Co., Ltd. This system merely relates to atechnology for handling RF signals that will be applied to an opticalmodule, but does not disclose the optical module itself.

SUMMARY OF THE INVENTION

An advantage of the present invention is to provide an optical modulecapable of realizing an optical transmitting part of a multiplexing andoptical transmit/receive function for a remote.

The present invention preferably provides an optical module withmultiplexer for optical transmission of remotes of an IMT-2000 digitaloptical repeater network having base stations, multiple remotespositioning downwards of said base stations, wherein said multipleremotes and are connected to a remote or a base station upwards andconnected to a main branch or sub-branches downwards.

The present invention is characterized by an optical transmitting partof said optical repeater comprises a function for data distributionthrough forward link, a function for dropping/adding data per sector, afunction for summing three data in respective sectors, and a functionfor data transmission through reverse link, and simply the high speedmultiplexing data is connected to the 1:16 bit deinterleaved data and16:1 bit interleaver before said high speed multiplexing data isdemultiplexed into low speed payload in the format of data transmissionin the forward link.

In the present invention it is preferable that said optical module withmultiplexer further include a PLL circuit as a narrow band pass filter,and said PLL circuit filters the clock extracted from the high-speedmultiplexing signals received from a forward link and said extractedclock is divided into 16 clocks and said divided clocks are supplied asa reference clock to all the clock generating and 16:1 bit interleaversand clock extraction and 1:16 bit deinterleavers of forward and reverselink.

The present invention provides an advantage of said optical module withmultiplexer further providing a drop/add selecting function.

The present invention provides a further advantage of said opticalmultiplexing signals are divided and transmitted in order to transmitsaid high-speed multiplexing signals downward to the main branch andsub-branch in the forward link by using an optical splitter, and saidoptical splitter distributes more optical power to the main branch ofthe optical link to be possibly by-passed than the sub-branch.

The present invention provides a still further advantage of said opticalmodule with multiplexer further providing a means for making the addeddata and dropped data delay in a corresponding repeater to the extent ofa predetermined time for a smooth handover between remotes.

Other purposes and merits of the present invention will be clarifiedafter reading the detail description of the invention and referring tothe attached drawings.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a general network structure for an IMT-2000 digital opticalrepeater;

FIG. 2 is a general structure of an optical transmitting part for aremote;

FIG. 3 is a structure of an optical module with multiplexer according tothe present invention;

FIG. 4 is wave diagram for payload data, clock signals andsynchronization signals used in the FIG. 3;

FIG. 5 is a structural view of the Mx/16 Hz PLL according to the presentinvention; and

FIG. 6 is a structural view of the elastic storing equipment accordingto the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Although a remote according to the present invention can process all thesignals of three sectors, for simplicity of explanation the embodimentbelow describes processing of only one sector.

The structure of an optical module with multiplexer according to thepresent invention is shown in FIG. 3. In the present invention, thehigh-speed multiplexing signals with Mx bits per second (bps)transmitting speed is formed by multiplexed low speed payload data thatare formed in n sequence of signals having Tr bps speed, and it includesoverhead bits formed by a frame align signal for forming frame, a paritybit signal for monitoring the transmission performance and datacommunication channel (DCC) bits. The payload data D(α, β, γ) isaccompanied with a clock signal CK that is synchronized to the payloaddata and a synchronization signal SYNC for indicating signal position inthe payload data that is not included in the high-speed multiplexingsignal data.

FIG. 4 shows a waveform of signals D (α, β, γ), CK, SYNC. That is, FIG.4 illustrates a wave diagram of the payload data, the clock and thesynchronization signal used in FIG. 3.

In order to multiplex the low speed payload data according to thepresent invention, 16 stages parallel framing with a processing speed ofMx/16 bps and parallel scrambling are executed, and then multiplexed tohigh-speed multiplexing signal by using 16:1 bit interleaver. And viceversa in the receiving part, payload data are separated to 16 sequencesof data signal by using 1:16 bit deinterleaver and realizing of 16stages of parallel reframing and parallel descrambling.

As the high-speed multiplexing signal received on the forward linkshould be transferred downwards to the main branch and sub-branchwithout change, the way to do this in the present invention isconnecting 1:16 bit deinterleaved signals of Mx/16 bps instead ofconnecting in the form of payload data that is used generally. By doingso, the present invention can minimize the signal delay generated in thesteps for de-multiplexing and multiplexing into the payload data and canobviate a circuit for multiplexing the payload data. An optical signalFOR received from a WDM coupler (202) is converted into 1:16demultiplexed 16 parallel signals F16D and parallel output clock signalsF16CK through an optical-to-electrical converter (203) and a clockextraction and 1:16 bit deinterleaver (204). In reverse processing, theF16D and F16CK become FOT signals identical to the FOR through a clockgenerating and 16:1 bit interleaver (205) and an electrical-to-opticalconverter (206).

Generally, optical signals to be transmitted downwards to main branchand sub-branch are made by an extra electrical-to-optical converter, andtransmitted downwards through WDM couplers (226, 227) respectively afterdistributing optical power of FOT signal by an optical splitter (207) inthe present invention to reduce the usage of the expensiveelectrical-to-optical converter. At this time, the optical splitter(207) is controlled to distribute more optical power to main branchhaving long transmitting distance in case of a bypassing by differentlydistributing to main branch and sub-branch like 2:1.

By providing a clock of Mx/16 Hz RCK cleaned by suppressing jitter ofMx/16 Hz F16CK by using a narrow band filter Mx/16 Hz PLL (208) as areference clock for a clock generating and 16:1 bit interleaver (205),the jitter of Mx bps multiplexed signal through the clock generating and16:1 bit interleaver (205) is made small. This improves transmissionperformance and maximizes the number of repeaters connected in cascadeby minimizing jitter accumulated through repeaters. The RCK is alsoprovided to the clock generating and 16:1 bit interleaver (226) inreverse direction as a reference clock, and then the jitter of Mx bpsmultiplexed signal is made to be small. Also, the RCK is provided toclock extraction and 1:16 bit deinterleaver (204, 217, 218) as areference clock obviating an extra clock oscillator.

FIG. 5 illustrates a structure of Mx/16 Hz PLL (208). The signals F16CKand RCK are equally divided (here divided into 8 parts) and theninputted to a phase detector (303). The output of the phase detector(303) is applied to a low pass filter (304) designed to have low enoughcutoff frequency and low enough jitter gain, and the low pass filtersupplies a control voltage of Mx/16 Hz VCXO (305), and then finally ajitter suppressed RCK, which is synchronized to F16CK is obtained. Forthis jitter reducing PLL VCXO (voltage controlled crystal oscillator) isadequate to applied because it is insensitive to noise due to its smallgain.

In FIG. 3, at the same time of transferring data in the forward link tothe next remote without change, in order to select and drop payload ofan assigned sector to a remote, the F16CK and F16D is inputted again tothe reframe and de-scrambler (209), and the payload data D (α, β,γ)_(FWD) with its accompanied data CK_(FWD), SYNC_(FWD) are extracted.Finally through the drop selector (210) the payload signal DRD′ of anassigned sector and its accompanied DRCK′ and DRSYNC′ are selected fromD (α, β, γ)_(FWD) which contains all sector signals.

Since the dropped signal outputted from the drop selector is processedwith gapped clock F16CK extracted from FOR signal received in forwardlink, the data has irregular period, i.e. the data has the informationonly at valid time slots.

This data of irregular period becomes a DO(−)_(FWD) transformed to datawith smoothed Tr bps period, its synchronized smoothed clock DOCK_(FWD)and synchronizing signal DOSYNC_(FWD) through the elastic store (211).FIG. 6 shows the structure of the elastic store (211) according to thepresent invention.

If the buffer in the elastic store (211) has m stages, inputted gappedclock DRCK′ and the output DOCK_(FWD) of Tr Hz VCXO (406) are equallydivided and then inputted to a phase detector (404).

The output of the phase detector controls VCXO (406) in voltage througha low pass filter (405) designed to have low enough cutoff frequency andlow enough jitter gain, and then jitter suppressed Tr Hz DOCK_(FWD)having smoothed period is generated.

By using the smoothed clock DOCK_(FWD), smoothed data DO(−)_(FWD) andDOSYNC_(FWD) are read and then outputted. In an elastic buffer with mstages, each buffer is written by Tr/m Hz clock and then read with timeinterval. Due to the characteristics of the PLL removing the phasedifference in FIG. 6, the phase relation between WCK and RCK may bemaintained, and time difference between the writing clock and thereading clock by using this phase relation can be controlled to bemaximized.

The multiplexed optical signals ROR1 and ROR2 received through the WDMcoupler of (213, 214) of FIG. 3 are inputted into clock extraction and1:16 bit deinterleaver (217, 218) through the optical-to-electricalconverter (215, 216). In the clock extraction and 1:16 bit deinterleaverof (217, 218), parallel clocks of Mx/16 Hz, R16CK1 and R16CK2, 16parallel data signals R16D1 and R16D2 are outputted. The parallel datawith a parallel clock are reframed and descrambled at the reframe andde-scrambler of (219, 220) and are demultiplexed, and generate payloaddata D1(α, β, γ)_(RVS) and D2(α, β, γ)_(RVS) output respectively. Thepayload data D1 (α, β, γ)_(RVS) and D2 (α, β, γ)_(RVS) are accompaniedby CK1 _(RVS), SYNC1 _(RVS) and CK2 _(RVS), SYNC2 _(RVS) respectively.The added data DO(−)_(RVS) and the drop data DO(−)_(FWD) at the remoteare delayed in the delay (221, 222) respectively to the extent ofpredetermined time for a good handover between each remote.

The delay controlled add data to a predetermined time should bephase-aligned to 2 groups of payload data received from the main branchand the sub-branch to sum them in respective sectors. A phase aligner(222) aligns the 3 sectors' payload data based on a reference signal ofDOCK_(FWD) and DOSYNC_(FWD) outputted from an elastic buffer (211). Thepayload data signal of the corresponding remote DO(−) passed through thephase aligner (220) is inputted only into a corresponding sector's portof 3 sectors of the summer (224). This is to choose DO(−) signal at aninput port connected to the add selector (223) and summer (224) so thatthe chosen signal is effective only in one of DO(α), DO(β), DO(γ). Theadder (224) outputs signals DS(α), DS(β), DS(γ) that are signals made bysumming data in respective sectors. The summed data are multiplexed into16 parallel signals of R16DS with R16CK of Mx/16 Hz clock forming aframe by the frame and scrambler (225) and are transformed to high-speedmultiplexing signals by the clock synthesizing and 16:1 bit interleaver(226), and is transmitted over the reverse link through theelectrical-to-optical converter (227).

Advantages of the present invention include minimizing the signal delayminimized by directly connecting the 16 data sequences obtained through1:16 bit deinterleaving to 16:1 bit interleaver before demultiplexingthe high-speed multiplexing signals to payload data in order to transfersignals received from the upper side to the next remote in the forwardlink. The optical repeater module according to the present invention canalso obviate the frame and scrambler circuit for multiplexing payloaddata in relaying the data, and can minimize the jitter accumulation innetwork, after filtering parallel clocks with 16 divided parts by usingPLL having high Q value and making clock with reduced jitter, byproviding the clock with reduced jitter as a reference clock to theclock generating and 16:1 bit interleaver for the forward and reverselink.

The optical repeater module of the present invention can function forselecting a corresponding sector signal for a remote's dropping/addingand a function for summing data of 3 sectors in respective sectors,making it unnecessary to have an extra external circuits for thesefunctions and signal interfacing circuits.

Also, in the optical repeater module of the present invention, the delayfunction of the added data for a handover is executed in the opticalrepeater module and so it is not necessary to have extra externalcircuits to do that.

Additionally, the optical repeater module of the present invention canminimize the use of the clock generator and the voltage control crystaloscillator by providing a clock from one Mx/16 Hz PLL as a referenceclock simultaneously to all of 2 clock generator and 16:1 bitinterleavers for high-speed multiplexing in the forward and reversedirection, and to all of 3 clock extractor and 1:16 bit deinterleaversfor extracting clocks from high-speed multiplexing signal received inthe forward and reverse direction.

It will be recognized that the invention can be modified and implementedin various forms that are not limited to the specific embodiments shownin the detailed description of this invention. The present invention isnot confined to the embodiments described above, but rather includes allthe modifications and replacements within the scope and sprit of thefollowing claims.

1. An optical module with multiplexer for optical transmission for aremote of an IMT-2000 digital optical repeater network having basestations, multiple remotes positioned downwards of said base stations,wherein said multiple remotes are connected to a remote or a basestation upward and connected to a main branch or sub-branch, comprisingan optical transmitting part of said optical repeater that functions fordata distribution through a forward link, for dropping/adding data persector, for summing three data sectors in respective sectors, and fordata transmission through a reverse link, wherein high speedmultiplexing data is connected to 1:16 bit deinterleaved data and a 16:1bit interleaver before said high speed multiplexing data isdemultiplexed into low speed payload in a format of data transmission inthe forward link.
 2. The optical module with multiplexer as set forth inclaim 1, further comprising a PLL circuit as a narrow band pass filter,and said PLL circuit filters a clock extracted from the high-speedmultiplexing signals received from the forward link and said extractedclock is divided into 16 clocks and said divided clocks are supplied asa reference clock to all clocks for generating 16:1 bit interleavers andclocks for extracting 1:16 bit deinterleavers of the forward and reverselinks.
 3. The optical module with multiplexer as set forth in claim 1,further comprising a drop/add selecting function.
 4. The optical modulewith multiplexer as set forth in claim 3, wherein said opticalmultiplexing signals are divided and transmitted to transmit saidhigh-speed multiplexing signals downwards to the main branch andsub-branch in the forward link by using an optical splitter, whereinsaid optical splitter distributes more optical power to the main branchof the optical link to be possibly by-passed than the sub-branch.
 5. Theoptical module with multiplexer as set forth in claim 4, wherein saidoptical module with multiplexer further comprises a means for delayingadded data and dropped data in a corresponding repeater to the extent ofa predetermined time for a smooth handover between remotes.
 6. Anoptical module with multiplexer for optical transmission of a remote ofan IMT-2000 digital optical repeater network having base stations,multiple remotes positioned downward of said base stations, wherein saidmultiple remotes are connected to a remote or a base station upward andconnected to a main branch or sub-branches downwards, and the high-speedmultiplexing signal has a transmission speed of Mx bits per second (bps)and is a multiplexed signal of low-speed payload data consisting of nsignal sequences having a transmission speed of Tr bps, and thehigh-speed multiplexing signal includes a frame align signal for forminga frame, a parity bit signal for monitoring transmission performance, anoverhead consisting of data communication channel bits, and the payloaddata accompanies a clock signal CK synchronized to the payload data anda synchronization signal SYNC for marking signal position in the payloaddata that is not included in the high-speed multiplexing signal data,said optical module with multiplexer comprises: a first WDM coupler forinputting high-speed multiplexing signal transmitted from the upwardside of a donor; a first optical to electrical converter for convertingan optical signal FOR received by said first WDM; a first clockextraction 1:16 bit deinterleaver for bit demultiplexing to 1:16 afterextracting clocks from output signals of said first optical toelectrical converter; a first reframe and descrambler for extractingpayload data with overhead bit by getting frame synchronization afterinputting 16 parallel data received from said first clock extraction and1:16 bit deinterleaver; a drop selector for selecting only payload datacorresponding to a specific sector by inputting payload data receivedfrom said first reframe and descrambler; an elastic store fortransforming data with irregular period inputted from the output signalof the drop selector to smoothed data; a first delayer for delaying tothe extent of a predetermined time by inputting dropped signalD₀(−)_(FWD) from said elastic store in order to compensate thetransmitting time difference between repeaters; a first clock generating16:1 bit interleaver for multiplexing to serial data from 16 paralleldata by using Mx Hz clocks synthesized for high-speed multiplexing witha reference of Mx/16 Hz clock from the output signal of said first clockextraction and 1:16 bit deinterleaver; a first electrical to opticalconverter for converting output signals of said first clock generating16:1 bit interleaver to optical signals; an optical power splitter forsplitting the output signals of said first electrical to opticalconverter to a second and a third WDM couplers; a second optical toelectrical converter for inputting optical multiplexing signals ROR1from said second WDM coupler for inputting the output signals split bysaid optical power splitter and payload data received from the mainbranched path; a third optical to electrical converter for inputtingoptical multiplexing signals ROR1 from said third WDM coupler forinputting the output signals split by said optical power splitter andpayload data received from the sub-branched path; a second clockextraction and 1:16 bit deinterleaver for extracting clocks from theoutput signals of said second optical to electrical converter and forbit demultiplexing to 1:16; a third clock extraction and 1:16 bitdeinterleaver for extracting clocks from the output signals of saidthird optical to electrical converter and for bit demultiplexing to1:16; a second reframe and descrambler for receiving Mx/16 Hz R16CK1parallel clocks from said second clock extraction and 1:16 bitdeinterleaver and 16 parallel data signals R16D1; a third reframe anddescrambler for receiving Mx/16 Hz R16CK2 parallel clocks from saidthird clock extraction and 1:16 bit deinterleaver and 16 parallel datasignals R16D2; a second delayer for delaying to the extent of apredetermined time by inputting added data D₀(−)_(RVS) at acorresponding repeater in order to compensate the transmitting timedifference between repeaters; a phase aligner for inputting the outputsignals of said elastic store, said second and said third reframe anddescramble in order to align the phases each other and to add the timedelayed adding data by through said second delayer to 2 groups ofpayload data received from the main and sub-branched paths; an addselector for classifying the payload data made from remotes and inputtedby said phase aligner to each sector in order to add to payload datareceived from the reverse link; a summer for summing the payload datamade by the remotes and the payload data received through a reverse linkin respective sectors by inputting the output signals of said addselector and the output signals of said phase aligner; a framer andscrambler for forming frame by inputting the outputs of said elasticstore and said summer and multiplexing to Mx/16 Hz clock R16CK signalsand 16 parallel signals R16DS; a second clock generating and 16:1 bitinterleaver for transforming to high-speed multiplexing signals byinputting the output signals of said framer and scrambler; a narrow-bandfilter Mx/16 Hz PLL for providing a reference clock to said first andsaid second clock extraction and 1:16 bit deinterleaver, said first andsaid second clock generating and 1:16 bit deinterleaver and said framerand scrambler by jitter-suppressing Mx/16 Hz F16CK inputted from saidfirst clock extraction and 1:16 bit deinterleaver and generating a clearclock RCK; and a second electrical to optical transformer fortransforming to said first WDM coupler through a reverse link byinputting the high-speed multiplexing signals from said second clockgenerating and 16:1 bit inverter.
 7. The optical module with multiplexeras set forth in claim 6, wherein said elastic store comprises: anm-stage elastic buffer for equally dividing an un-smoothed clock DRCK′and D0CK_(FWD) output of Tr Hz VCXO into m clocks and outputting saiddivided clocks to a first phase detector (PD); and a first low passfilter (LPF) for making jitter suppressed Tr Hz D0CK_(FWD) having auniform period by inputting the output of said first phase detector andcontrolling the input voltage of said VCXO.
 8. The optical module withmultiplexer as set forth in claim 6, wherein said Mx/16 Hz PLLcomprises: two frequency dividers for equally dividing said F16CK andRCK respectively; a second phase detector for inputting the output ofsaid dividers; a second low pass filter for inputting the output of saidsecond phase detector; and an Mx/16 Hz VCXO (Voltage Controlled CrystalOscillator) for producing RCK signal jitter-suppressed and synchronizedto F16CK from the output of said second low pass filter.